Seasonality and the serotonin transporter promoter repeat length polymorphism

Leo Sher, M.D.

Our research note, “Seasonality associated with the serotonin transporter promoter repeat length polymorphism” was published in the November 1999 issue of the American Journal of Psychiatry (1).

The propensity of people to exhibit changes in mood and behavior with the changing seasons, also known as seasonality, can be viewed as a continuum ranging from those who show no seasonal changes to those who exhibit extreme changes with the seasons. It was previously observed that the short allele of the serotonin transporter promoter repeat length polymorphism is associated with seasonal affective disorder, and in patients with seasonal affective disorder, the short allele is associated with higher levels of seasonality than in those with the long allele (2).

In this study, we investigated the association between the serotonin transporter promoter repeat length polymorphism and seasonality in a general population sample. The Seasonal Pattern Assessment Questionnaire was administered to 209 Caucasian individuals who were selected from the general population.

The global seasonality mean score for the long-long genotypes was significantly lower in comparison to the mean score for the non-long-long genotypes. We found no difference in seasonality mean scores between those who were heterozygous and those who were homozygous for the short allele. Our study has shown that the serotonin transporter promoter repeat length polymorphism may influence seasonality and that higher seasonality scores take place in individuals with at least one short allele.

References

  1. Sher L, Hardin TA, Greenberg BD, Murphy DL, Li Q, Rosenthal NE. Seasonality associated with the serotonin transporter promoter repeat length polymorphism. Am J Psychiatry 1999 Nov;156(11):1837.
  2. Rosenthal NE, Mazzanti CM, Barnett RL, Hardin TA, Turner EH, Lam GK, Ozaki N, Goldman D. Role of serotonin transporter promoter repeat length polymorphism (5-HTTLPR) in seasonality and seasonal affective disorder. Mol Psychiatry 1998; 3:175–177.